1. Field of the Invention
This invention relates to sprocket configurations and in particular to chain drive sprocket configurations.
2. Description of the Prior Art
In vehicle chain drives, sprockets are utilized over which the chain is trained for guiding the chain in the driving operation. The sprocket defines a plurality of teeth which are engaged by the respective bushings being received in the pockets between the teeth as the chain passes in engagement with the sprocket.
In the conventional sprocket configuration, wear may occur both in the sprocket and the bushing because of accumulation of foreign matter in the pockets tending to urge the chain outwardly from the bottom of the pocket and thereby cause an elongation of the chain in the driving operation.
The outward movement of the chain relative to the pocket causes the bushings to make contact with the outer portions of the sprocket teeth. Heretofore, the sprocket teeth have had relatively sharp corners and the engagement of the bushings therewith has heretofore caused severe wear of the bushings as a result of the tooth pocket packing and resultant outward displacement of the chain.
A number of attempts have been made to solve this vexatious problem. Thus, in U.S. Pat. No. 2,667,792 of Wilfrid H. Bendall, an improved pivoted link chain drive is disclosed having a plurality of spring members engaging the link members of the chain for holding the pivot center of each link and its following drive strand on a centerline substantially tangent to the sprocket pitch circle during all phases of pivotal engagement of the link with the tooth of the sprocket. This structure is taught as reducing the sprocket engagement impact of pivoted link chains for providing improved operation over a wide speed range.
In U.S. Pat. No. 3,194,609 of Lloyd Thurlow, a tractor is shown as provided with a chain drive having a sprocket and roller-type chain. The effective sprocket pitch is taught to be less than that of the chain with the pocket radii being on the pitch line. Thus, the configuration of the Thurlow patent is directed to permitting the chain drive to operate satisfactorily as long as the pitch diameter of the chain is in the range of the pitch diameter of the sprocket to an imaginary sprocket having the same effective pitch as that of the chain.